Cracking of hydrocarbons



Patented Aug. 31, 1948 CRACKING F HYDROCARBONS Robert E. Burk, ClevelandHeights, Ohio, assignor to The Standard 0i] Company, Cleveland, Ohio, acorporation of Ohio No Drawing. Application December 12, 1942,

Serial No. 468,813

1 Claim. (01. 196-52) This invention relates to the cracking ofhydrocarbons utilizing a catalyst comprising a mixture of hydrogenfluoride and boron trifluoride. The word cracking as used herein isintended to cover the ordinary simple cracking process in which thehydrocarbons produced by the cracking are not subjected to furtherchemical modiflcations in the process. 7

Hydrogen fluoride has been known to exert a catalytic action in certainprocesses involving reactions of hydrocarbonasuch as alkylations, buthydrogen fluoride as such is not a catalyst for cracking. Borontrifluoride also has been proposed as a catalyst for certain reactions,but it too when used by itself does not possess a catalytic activity forcracking.

Contrary to what might have been expected from a consideration of theindividual properties of these fluorides with respect to cracking, Ihave discovered that a mixture of hydrogen fluoride and borontrifluoride is a very active and effective cracking catalyst.

Accordingly, it is an object of my invention to crack hydrocarbons underappropriate temperature and pressure conditions with a catalystcomprising both hydrogen fluoride and boron trifluoride.

The use of the novel catalyst for cracking is particularly advantageousin that the extent and nature of the activity may be varied andcontrolled by altering the proportions of hydrogen fluoride and borontrifluoride. This control, when used in connection with variations intemperature and pressure, permits a wide range of operations andresults. It also adapts my cracking process to a large number of rawmaterials to be cracked, and makes it possible to produce a wide varietyof cracked products.

The catalyst to be employed in accordance with the invention may be amixture of the fluorides in any of a wide range of proportions.Preferably, the amount of hydrogen fluoride is in excess of the amountof boron trifluoride and in such a case the catalyst may be regarded ashydrogen fluoride promoted with boron trifluoride.

Hydrogen fluoride boils at 67 F. and therefore may readily exist in aliquid or gaseous phase depending on the temperature and pressure. It isthus admirably suited for either a liquid or vapor phase crackingprocess. Boron trifluoride has a boiling point of -150 F. and thereforeexists as a gas at the temperatures usually encountered. However, it maybe dissolved in the liquid hydrogen fluoride and thus the mixture mayexist and be used in either the liquid or gaseous phase. The relativeproportions of the two fluorides in the catalyst can be readilydetermined by measurin the partial pressure of the boron trifluoride inthe mixture, and the amount present during a cracking process may becontrolled in the same way. a

The relative proportions of the hydrogen fluoride and the borontrifluoride in the catalyst may be varied over a wide range depending onthe rate of reaction desired, temperature, pressure, stock beingtreated, products wanted, etc. The inter-relation of these factors iswell understood in the cracking art. In general, the higher theproportion of boron trifluoride present as a promoter, the greater willbe the cracking activity of the catalyst, and an eflicient operation ona commercial scale will generally require a substantial amount. In apreferred embodiment of my invention, the amount of boron trifluoridemay vary from to 50% of the amount of hydrogen fluoride on a molal basisregarding hydrogen fluoride as HF and boron trifluoride as BFs.

The amount of the catalyst used may vary over a widerange depending uponthe temperature and pressure conditions, the stock being treated, theproducts wanted, etc., as will be understood by those skilled in thecracking art, In general the range will be 5 to 300% of the hydrocarbonto be cracked.

The hydrocarbons that may be cracked in accordance with the processcomprise primarily those of the aliphatic paraffin series and generallythe cracking is applied to paraffin hydrocarbons of six or more carbonatoms. The cracking process, however, may also be applied to ringcompounds having one or more crackable side chains, to cycloparaflins,or to mixtures of any of the above.

Because of the tendency of the catalyst to form a complex or a loosechemical combination with aromatics, or to be absorbed by them, thecatalytic cracking process of the invention is readily adapted tohydrocarbons low in aromatics. However, if larger amounts of thecatalyst are used, so that there is an excess of the catalyst to beeffective for cracking the unabsorbed paraffin hydrocarbons, the processmay be used directly with aromatic containing hydrocarbons, and crackingof the side chains on the aromatics, if any, accomplished simultaneouslywith the cracking of the paraflins.

If desired an aromatic containing hydrocarbon may be dearomatized and/orunsaturated components removed by extraction with selective solvents orby any other process. Alternatively such hydrocarbons may be treatedfirst with the catalyst in liquid form at a low temperature, to removethe aromatics as a separate fraction, as described in my earlier filedcopending application Serial No. 423,303, filed December 17, 1941,Patent Number 2,343,744. The dearomatized hydrocarbon may then becracked with the catalyst. The aromatics may have any side chainscracked or may be recovered from the separated fraction and cracked orotherwise treated or utilized.

After the cracking operation the catalyst may be recovered bystratification if a liquid phase operation is used, or by absorption orreaction with various chemicals as the economics and the needs of theparticular process dictate.

When the process is applied to cracking in the liquid phase, atemperature of from to +450 F. may be used, ambient temperatures beingpreferred because of convenience. The pressure may vary from atmosphericpressure to at least 1000 pounds per square inch. When highertemperatures are used in a liquid phase operation it will be understoodthat sufiicient pressure must be used to keep the hydrocarbon to becracked and the catalyst in a liquid phase.

When the process is applied to cracking in the vapor phase thetemperatures preferred are Within the range of 100 to 900 F. andpressures used may vary from atmospheric to at least 1000 pounds persquare inch.

The catalyst is also adapted for a combination liquidevapor phasecracking process in which the hydrocarbon to be cracked is in the liquidphase and the catalyst is in the vapor phase, and may, for example, bepassed countercurrent under appropriate conditions of temperature andpressure to maintain the hydrocarbon and catalyst in these phases.

In either liquid or vapor phase cracking, the temperature and pressureto be selected will depend in part upon the amount of catalyst and therelative proportions of the fluorides it is decided to use, and upon thestock to be cracked and the products wanted. The economics involved ineach of the factors must also be considered in a commercial operation.Cracking processes using catalysts are well understood in the petroleumart, and the various techniques, procedures, the conditions of operationand types of apparatus used therein are well known and so diverse as tomake it unnecessary and impractical to describe them in infinite detailin order that a person skilled in the art may successfully practice myprocess.

The following example is given merely as illustrative of the desirableresults that may be obtained in accordance with the process, and not asa limitation on the above defined scope ofthe invention, nor as anattempt, to illustrate the diversity of the application of my process.In accordance with this example a dearornatized Pennsylvania kerosenewas subjected at av pressure of 18.5 pounds. per square inch totalpressure at a temperature of 90 F. to a treatment with 8.9% by volume ofhydrogen fluoride containin boron trifluoride in an amount. to; yield apartial pressure of 15.0 pounds p r squar in h. After treatment forabout two hours, two layers separated, the upper yielding about 30 percent gasoline (based on the kerosene cracked), about 34 percentisobutane and less than 2.5% normal butane, propane and products of lessthan 3 carbon atoms. The product in the lower layer, upon separationfrom the catalyst, was a drying oil capable of drying to a hard finish.It will be seen that my process results in a good yield of particularlyvaluable products, namely gasoline and isobutane, and that theunsaturates formed are readily utilizable.

Further illustrative examples show that at higher temperatures theyields of gasoline are somewhat lower and an appreciable amount ofpropane and normal butane are also formed. Lower temperatures giveincreased yields of gasoline and a smaller amount of isobutane and. alsosmaller amounts of products in the lower layer with the catalyst.

This application is a continuation in-part of my co-pending applicationSerial No. 423,073, filed December 15, 1941.

From the above description it will be seen that my process is subject tomany variations and embodiments and I intend all of the same to he.included within my invention as one within the following claim:

I claim:

The process of catalytically cracking hydrocarbons, which comprisestreating kerosene with a liquid catalyst the inorganic constituents ofwhich comprise primarily about 89 volume per cent of hydrogen fluoride(based on the kerosene) promoted by an amount of boron trifluoridedissolved therein to provide a partial pressure of boron trifluoride ofabout 150 pounds per square inch, at a. temperature of about 90 F., andat a pressurev at least sufiicient to maintain the hydrogen fluoride inthe liquid phase at said temperature, and continuing the treatment for aperiod of time under the above conditions such that cracking of thekerosene to. produce a. substantial amount or gasoline and lowerhydrocarbon-s is the principal reaction.

ROBERT E. BURK.

REFERENCES CITED be following referencesare of record in the file ofthis patent:

UNITED STATES PrYIEN'fFSv Number Name Date 2,172,146 Ruthrufi Sept. 5,1939 2,216,274 Grosse Oct. 1, 1942 2,320,629 Matu-szak June I, 1943'2,337,432 Veltman Dec. 21E, 1943' 2,344,789 Schmerlin-g Mar; '21, 19442,357,495 Bloch Sept. 5, 1944 i FOREIGII PATENTS Number- Country Datev292,932: Great Britain May .23, 1929:

OTHER REFERENCES Sacha-pen, Qonversion of Petroleum, 19.40 Reinhold Pub.Corp... New York, pages 198499.

